Tool for roughening a borehole surface

ABSTRACT

A tool for roughening a borehole surface. The tool includes a coupling portion for clamping the tool in a drilling machine; and a tool head for machining the borehole surface, where the tool head has an outer shell surface on which a cutter protrudes laterally from the shell surface, and where the outer shell surface has a camber along the longitudinal direction of the tool.

The invention relates to a tool for roughening a borehole surface, with a coupling portion for clamping the tool in a drilling machine and a tool head for machining the borehole surface, wherein the tool head has an outer shell surface on which cutting means are disposed.

For fastening building parts to foundations, it is known to fix profiled anchor bars by means of a chemical mortar compound in blind holes already drilled into the foundation. The blind holes can be drilled by means of diamond-surfaced tools. Depending on the material of the foundation, the borehole wall of such a borehole may be very smooth. In order to transfer even high tensile forces acting on the anchor bars reliably to the foundation, it is of advantage when the mortar compound in the cured condition interacts interlockingly with the borehole wall. This can be achieved by roughening at least part of the borehole wall or by providing it with profiling.

Tools and methods of the type mentioned in the introduction for roughening a borehole surface are therefore used in particular to increase the load-bearing capacity of chemical mortar compounds in diamond-drilled holes. In the process, the relatively smooth inner shell surface of a borehole is structured and, for example, provided with defined undercuts.

DE 31 43 462 A1 and DE 38 19 650 A1 respectively describe tools on the tool shank of which a separate conical contact face is provided, to enable a user to superpose a wobbling motion manually on the tool rotation. In this way, the tool head is deflected in radial direction and penetrates into the borehole surface.

The already known solutions suffer from the disadvantage that the manufacturing process is complex because of the contact faces provided separately on the tool shank, and so the tools are expensive.

Against this background, the technical problem underlying the present invention is to specify, for roughening the surface of a borehole, a tool that does not exhibit the disadvantages described in the foregoing or at least exhibits them to a lesser extent, and in particular permits roughening of a borehole surface in simple and cost-effective manner.

The technical problem described in the foregoing is solved by a tool for roughening a borehole surface, with a coupling portion for clamping the tool in a drilling machine and a tool head for machining the borehole surface, wherein the tool head has an outer shell surface on which cutting means protruding laterally from the shell surface are disposed. The outer shell surface has a camber along the longitudinal direction of the tool.

Due to the cambered structure of the shell surface, uniform machining of the borehole surface is favored during the roughening process. Thus a user is able to introduce the tool head into a borehole to be machined and to superpose a swiveling or stirring motion manually on the tool rotation generated by the drilling machine. In the process, the cambered outer contour of the tool head can be used as a guide surface for a swiveling motion of the user. For example, the tool may be moved from a first angular orientation to a second angular orientation by making the cambered tool head roll over the borehole surface along the longitudinal direction of the tool. Here, a change between two angular orientations means swiveling of the longitudinal axis of the tool relative to a longitudinal or center axis of the borehole.

According to an improvement of the tool, the shell surface has a maximum diameter, which is disposed centrally with respect to a longitudinal extent of the tool head. In this way, uniform guidance of the tool by the user is favored during swiveling of the tool. Thus, starting from a maximum diameter, the camber of the shell surface can be configured particularly symmetrically, and the outer contour can describe a circular-arc segment, for example, in a cross section along the longitudinal axis of the tool.

The cutting means of the tool may comprise pins of a cutting material, especially carbide or diamond, wherein the pins are distributed circumferentially with an angular spacing. By means of the pins, it is possible to introduce undercuts into the borehole surface. In addition, especially if the pins are arranged circumferentially with constant angular spacing, the guidance of the tool during the roughening process can be improved.

Thus the pins may be disposed with an angular spacing with respect to the longitudinal axis of the tool, wherein the angular spacing is 30° to 180°, preferably 60° to 150°, more preferably 120°. For example, at least three pins may be distributed at an angular spacing of 120° on the outer shell surface of the tool head. In this way the wear of the tool head can be reduced, since the contact of the tool head with the borehole surface is largely determined by the pins and consequently wear of the outer shell surface carrying the pins is reduced.

According to a further configuration of the tool, the maximum diameter of the tool head is smaller than the nominal diameter of a borehole to be machined. For example, the maximum diameter of the tool head may be defined by carbide pins which, disposed on the cambered shell surface, describe an envelope circle with a diameter smaller than the nominal diameter of the borehole to be machined. This configuration permits simple introduction of the tool head into the borehole to be machined and in addition favors a swiveling or stirring motion by the user, since a clearance in radial direction is formed between the tool head and the borehole surface.

According to an improvement of the tool, the coupling portion is disposed at a first end of a tool shank and the tool head at an opposite, second end of the tool shank, wherein the tool shank has a diameter smaller than that of the tool head. Consequently, the tool shank is offset in radial direction relative to the tool head. A clearance is therefore formed between the tool shank and the borehole surface, and so free space is created for the user to guide the tool.

According to an improvement of the tool, the tool shank is at least as long as the tool head in axial direction. The tool is therefore also suitable for machining boreholes in the region of the borehole bottom, wherein the borehole depth corresponds to twice the axial length of the tool head.

The axial length of the tool head may correspond to at least nine times the maximum diameter of the tool head. With such a tool, it is possible to ensure that the roughened region of the borehole surface extends over a sufficient length in axial direction. Especially for drilling of blind holes, there is no need to blow out or clean the borehole despite accumulation of drilling dust in the region of the borehole bottom, since an adequately large roughened surface is available. Preferably, the tool head can be equipped with carbide or diamond pins distributed over its entire axial length.

According to a further configuration of the tool, the axial length of the tool head may correspond to at least nine times the nominal diameter of a borehole to be machined. With such a tool, it is ensured that the roughened region of the borehole surface extends over a sufficient length in axial direction. Especially for drilling of blind holes, there is no need to blow out or clean the borehole despite accumulation of drilling dust in the region of the borehole bottom, since an adequately large roughened surface is available. Preferably, the tool head may be equipped with carbide or diamond pins distributed over the entire axial length.

The largest diameter of the tool head should be at least 30% larger than the diameter of a tool shank joining the tool head and the coupling portion.

The invention will be described in more detail hereinafter on the basis of a drawing that schematically illustrates exemplary examples, wherein:

FIG. 1 shows a first configuration of an inventive tool in a perspective view, a front view and a side view; and

FIG. 2 shows a second configuration of an inventive tool in a perspective view, a front view and two side views.

FIG. 1 shows a tool 10 for roughening a borehole surface (not illustrated) in a perspective view, a front view and a side view. Tool 10 has a coupling portion 12 for clamping tool 10 in a drilling machine (not illustrated) and a tool head 14 for machining a borehole surface. Tool head 14 has an outer shell surface 16. Cutting means 18, which project radially relative to shell surface 16, are disposed on outer shell surface 16. Outer shell surface 16 has a camber along the longitudinal direction a of the tool, as is apparent in side view.

Shell surface 16 has a maximum diameter D1, which is disposed centrally with respect to the longitudinal extent of tool head 14. Starting from maximum diameter D1, shell surface 16 tapers in the direction of a front end 20 and an opposite end 22 at the shank, respectively to a minimum diameter D2 smaller than diameter D1. In other words, the outer shell surface in side view is bowed outward in a radial direction r.

The cutting means provided on shell surface 16 comprise carbide pins 18, which are distributed circumferentially with an angular spacing of 120° and also axially along longitudinal axis A of the tool.

The axial longitudinal extent of tool head 14 is larger than nine times the maximum diameter D3 of the tool head. Maximum diameter D3 of tool head 14 is determined by the diameter of the envelope circle of those carbide pins 18 that are disposed in the region of maximum diameter D1 of the shell surface.

According to alternative configurations of the invention, the axial longitudinal extent of the tool head is larger than nine times the nominal diameter of the borehole to be machined.

Coupling portion 12 is disposed at a first end of a tool shank 24 and tool head 14 at an opposite, second end of tool shank 24. Tool shank 24 has a diameter smaller than that of tool head 14. The axial length of tool shank 24 corresponds substantially to the axial length of tool head 14.

For roughening of a borehole surface (not illustrated), the inventive tool 10 is clamped in a drilling machine (not illustrated). Tool 10 is introduced together with the tool head into a borehole (not illustrated). In this connection, the nominal diameter of the borehole is preferably larger than the maximum diameter D3 of tool head 14. The drilling machine executes rotation of tool 10, while a swiveling or stirring motion is superposed on this rotation by the user. Cambered tool head 14 is guided by the user along the borehole surface, so that the guidance of tool 10 is predetermined by the shape of tool head 14. In this way, uniform roughening of the borehole surface can be achieved. In addition, due to the circumferential distribution of carbide pins 18, the wear of tool 10 in the region of outer shell surface 16 is reduced, especially at the height of maximum diameter D1.

FIG. 2 shows a further configuration of a tool 10, wherein this alternative configuration is characterized by a changed shape of coupling portion 12, which has a diameter larger than the shank diameter.

The tool is constructed such that the tool head has a largest diameter that is at least 30% larger than the diameter of the tool shank. 

1: A tool for roughening a borehole surface, comprising: a coupling portion for clamping the tool in a drilling machine; and a tool head for machining the borehole surface, wherein the tool head has an outer shell surface on which a cutter protrudes laterally from the shell surface, and wherein the outer shell surface has a camber along the longitudinal direction of the tool. 2: The tool according to claim 1, wherein the outer shell surface has a maximum diameter, which is disposed centrally with respect to the longitudinal extent of the tool head. 3: The tool according to claim 1, wherein the cutter comprises pins of a cutting material, and wherein the pins are distributed circumferentially with an angular spacing. 4: The tool according to claim 3, wherein the pins are disposed with an angular spacing with respect to the longitudinal axis of the tool, and wherein the angular spacing is 30° to 180°. 5: The tool according to claim 1, wherein the maximum diameter of the tool head is smaller than the nominal diameter of a borehole to be machined. 6: The tool according to claim 1, wherein the coupling portion is disposed at a first end of a tool shank and the tool head at an opposite, second end of the tool shank, and wherein the tool shank has a diameter smaller than that of the tool head. 7: The tool according to claim 6, wherein the tool shank is at least as long as the tool head in axial direction. 8: The tool according to claim 1, wherein the axial length of the tool head corresponds to at least nine times the maximum diameter of the tool head. 9: The tool according to claim 1, wherein the axial length of the tool head corresponds to at least nine times the nominal diameter of a borehole to be machined. 10: The tool according to claim 1, the largest diameter of the tool head is at least 30% larger than the diameter of a tool shank joining a tool head and coupling portion. 11: The tool according to claim 3, wherein the pins are disposed with an angular spacing with respect to the longitudinal axis of the tool, and wherein the angular spacing is 60° to 150°. 12: The tool according to claim 1, wherein the cutter comprises carbide or diamond pins, wherein the pins are distributed circumferentially with an angular spacing. 